A coke oven battery for producing coke by coking coal particles essentially comprises regenerative chambers 51 having a brick checkerwork therein disposed in the lower part thereof and intervening combustion (heating) flues 52 and coking chambers 53 disposed over said regenerative chambers, as shown in a partially exploded-perspective cross-sectional view in FIG. 14. Reference numeral 54 designates a coal charging hole provided in the top of each coking chamber. Reference numeral 55 denotes coke oven doors that close off and open up the entry- and exit-side openings of each coking chamber 53. The coke oven battery heats the coal particles charged into the coking chambers 53 by the combustion gas and air preheated in the regenerative chambers 51 and then burnt in the combustion chambers 52 adjacent to the coking chambers. The waste gas generated in the combustion chamber 52 flows to offtake stacks after passing through exhaust ducts (not shown) provided on the coking chambers 53 and then through flues 56 while heating the brick checkerwork in the regenerative chambers. The coke oven doors closing off and opening up the openings at the pusher and coke sides of the coking chambers are required to have a high enough heat resistance to withstand the high temperature (900° C. or above) at which the coal particles charged into the coking chambers are dry distilled and a high enough sealing ability to prevent the leaking of methane, carbon dioxide, hydrogen and carbon monoxide gases generated therein and the seeping of tar. Coke oven doors comprise approximately 400 mm thick heavy refractory blocks or bricks fitted in the pushing- and delivery-side openings of coking chambers and sealing members shaped like the cross-section of a knife edge pressed onto the door jamb, as disclosed in many Japanese patent gazettes such as Japanese Examined Patent Publication (Koukoku) No. 60-25072 and Japanese Unexamined Utility Model Publication (Kokai) NO. 5-56940. Recently, coke oven doors comprising refractory blocks or bricks adapted to plunge into the pushing- and delivery-side openings of coking chambers through seal plates were developed, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2001-288472, and are finding increasing use because of their effect to greatly decrease gas leakage during coking.
Made of heavy refractory blocks or bricks as described above, coke oven doors are capable of withstanding high temperatures and permitting long use. However, the refractory blocks or bricks of the coke oven doors that open up and close off the pushing- and delivery-side openings of coking chambers in every pushing is and release large quantities of heat when opened and absorb large quantities of heat when closed. Therefore, the coal particles charged near the coke oven door plugs are not heated high enough, as a result of which large quantities of undistilled poor-quality coke are generated. Thus it has been said that as much as 1.5 million tons of poor-quality coke are generated in Japan, which means there are a lot of waste of coal particles for the manufacture of coke and loss of heat energy. There have also been many other problems, such as collision and peeling of refractory blocks or bricks, mixing of peeled refractory blocks or brick fragments with coke, thermal damage of the coke oven door structure that might occur if peeled portions are left unrepaired, and removing of peeled blocks or bricks from delivered coke.
Many patent gazettes disclose coke oven doors newly developed with the improvement of coke oven heat efficiency in mind. For example, Japanese Examined Patent Publication (Koukoku) No. 03-40074 (Japanese application filed in 1985) discloses a “method for coking the charge in the coke oven by sending the hot gas generated by said charge to the gas passage through the vertical flue provided in at least one of the doors in contact with said charge and separated from the interior of the coke oven by the thermally conductive metal wall constituting said door and moving part of said hot gas to an upper end region in contact with said partition wall therethrough by the ascending of said gas and the heat conductivity of the partition wall”. A “coke oven door carrying on the inner side thereof a shield allowing passage of gases generated in the oven that comprises shielding members made up of spacers and coking plates” disclosed in Japanese Examined Patent Publication (Koukoku) No. 61-49353 (Japanese application filed in 1982) was developed based on the above-described method. Foreign patents similar to above mentioned Japanese patents are as follows. U.S. Pat. No. 4,381,972, U.S. Pat. No. 4,414,072, U.S. Pat. No. 4,467,342. Many other heat-up coke oven doors have been developed, such as a “coke oven door comprising a shield attached to the inner side of the oven wall via fittings to form a space for gas passage and made up of multiple shield members having vertically partitioned U-shaped cross sections” disclosed in Japanese Unexamined Patent Publication (Kokai) No. 62-72782 (Japanese application filed in 1985), a “coke oven door comprising heat-resisting packings attached to both sides of the coke oven walls comprising metal shields provided on the inside of the oven door proper via spacers to form a space for gas passage” disclosed in Japanese Examined Utility Model Publication (Koukoku) No. 06-43146 (Japanese application filed in 1988), and a “coke oven door with ceramic coking plates” disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. 02-69946 (Japanese application filed in 1988). Japanese Examined Patent Publication (Koukoku) No. 05-38795 (Japanese application filed in 1986) discloses a “coke oven door heated by raising the temperature of a gas space provided between a heat insulator attached to the oven door and a heating plate on the inner side of the oven by burning part of combustible gases generated by coking with the air and oxygen blown in from outside”.
Also, several coke oven doors having a gas flue to pass the gases generated in the oven or one incorporating a heating burner, in place of the conventional refractory bricks, on the coking chamber side thereof have been introduced as those promoting the temperature increase of coal particles charged near the coke oven doors. For example, Japanese Examined Utility Model Publication (Koukoku) No. 02-26913 and Japanese Unexamined Utility Model Publication (Kokai) No. 06-43146 disclose a coke oven door comprising a metal gas flue shield attached to the oven proper via a heat-insulating box made of a heat-insulating material covered with steel sheet”. Japanese Examined Patent Publication (Koukoku) No. 63-112686 discloses a “combustion type coke oven door that burns, in the gas space enclosed by metal shield, part of combustible gases generated during coking cycle with the air or oxygen blown in from outside. These newly developed coke oven doors are expected to decrease the generation of poor-quality coke and tar as they heat the coal particles near the coke oven door plugs by the high-temperature heat of the gases generated in the oven by providing shields or space boxes like gas flues to allow the passage of such gases to the coke oven doors. However, none of them have yet been put into practical use.
Though not certain, the inventor presumes that such coke oven doors have involved the following problems: Conventional space boxes comprise fabricated thin metal shield boxes. The space boxes have such structural problems as deforming under the influence of thermal stresses due to frequent heating and cooling repeated and cracking starting from metal sheet joints and propagating to other areas.